Process for purifying silicon.



' dation during the re-melting,

a solvent for the silicon dioxid as iron,

- these respects,

' gases.

FALLS CENTRE, ONTARIO,-CANAIDA, ASSIGNOR cremation a. race it ANK, or 1-:

HBO THE CARBOlB-UN'DUM COMPANY, OF NIAGA 1' 'EIOlll' 0F PENNSYLVA.

rcnss roe runr Ito Drawing.

chemical attack, high mechanical strength and freedom from porosity and gaseous occlusions are desirable.

The present process is'simple and inexpensive. It protects-the silicon against oxiand provides originally present asan objectionable impurity in the silicon. 7

Silicon metal as produced industrially in the electric furnace contains impurities such aluminum, "calcium and their com: pounds,cai'bon, silicon dioxid and occluded in this form the metal has a very coarse crystalline structure and is porous; consequently it is very brittle. and its mechanical strength is low. Remelting and casting the material does not improve it in but on the contrary, tends to make it more porous due tooxidation. While'silicon is not readily oxidized at a red heat, nevertheless at a white heat, or when fused, it is easily oxidized in; contact with coatedwith a layer of white oxid.

lack of homogeneity andpoor mechanical properties According to my invention, the elimination of impurities andprevention dioxide- 1. broken window glass.

v tio is efiected by melting the'si'licon in a crucible furnace,-or any. other nace, under a layer of slag, which lpreferably may be a natural or artlficial siji may be ordinary glass' melts besuitable fur cate, and WhlCll for convenience, 7 The fore thesilicon and flows over the surface, forming a layer which efi'ectually protects Specification of Letters Patent.

from silicon, which .silicon under a layer of a fused rams, NEW v0, a conse- Patented Apt. at, tare.

Application filed September 18, 1912. Serial No. 720,957.

the metal underneath from oxidation. The purification then complete in about three hours, the glass at the end of the run remaining as a dark slag. Metal so treated is, when cast, characterized by a dense and fine crystalline structure, by

perfect freedom from blowholes, and by considerable mechanical strength. An actual goes on rapidly and is very example of the results obtained is shown by r the following analysis in which column I is the composition of the silicon before purification, and column H is the composition after melting under silicate.

I. II.

Silicon 92. 05% 97. 47% Iron 4. 45 1. 20 Aluminum. 1. 80 33 (as used herein and in the claims) ll therefore mean not only commercial metallic silicon containing 9.0% and upward of silicon,

but also any alloy or compound in which silicon forms the principal constituent.

, Various methods may be employed in adding the silicate. It may be intimately mixed with the silicon before fusing or it may be added .ina molten state. lit may also be removed during the process and a fresh layer added. l have also employed other slags not containing silica, for exampleslags of fluor- Y s ar and have found that a certain eliminationof impurities is likewise obtained,

althoughll prefer to use slags of the silicate group. i v

ll claim: 1. The method of removing impurities consists in meltingtheslag adapted to unite with said impurities. p

considerable dimi- 2. The method of removing impurities- In testimony whereof, I have hereunto set from silicon, which consists in melting the myhand. silicon under a, layer of a fused silicate.

The methed of removing impurities CLARENCE J. BROCKBANK. 5 from silicon, which consists in melt ng the Witnesses:

silicon under a fused layer of a, double sili- EDMUND S. SMITH,

cate of calcium and an alkali metal. J. ROY LINCOLN. 

